Generally, cars produce driving power by burning gasoline or diesel and liquified natural gas or the like and using the explosive power therefrom to rotate a crank shaft, and have an internal combustion engine (hereinafter referred to as an “engine”) provided with a cylinder for compressing a mixture gas of fuel and air and burning the mixture gas. The engine is provided with a cylinder block which forms a plurality of cylinders, a cylinder head which is provided at a lower portion of the cylinder block and provides a combustion chamber, and a piston for an internal combustion engine which is configured such that the piston is installed within the cylinder to reciprocatively move up and down in the cylinder while carrying out the function of receiving a gas pressure in a high temperature and pressure generated in the process of expansion resulting from the explosion of the mixture gas and transferring it through a connecting road to the crank shaft. This piston for an internal combustion engine comprises a crown part, a boss part and a box part, and is made by using a piston mold apparatus.
Meanwhile, weight of the piston which reciprocatively moves in the cylinder of the engine acts as inertial force to have a significant influence on the designed strength and endurance of each constituent components of the engine. Thus, efforts for reducing the weight relative to the boss and box parts of the piston are continuing focusing on parts which scarcely have a large effect on the designed strength and endurance.